Need Server side alternative to Session Variables - to track "next available number"

I've got a Purchase Requisition web form that pulls the top Requisition Number from the database;

TopReqID = reader("ReqID")

and puts the next available Req Number in a label on the page;

lblPurchaseRequisitionNumber.Text = TopReqID + 1
That number, TopReqID + 1, with then, of course be the next ReqID key value entered once the form is submitted.

The ReqID is the Identity Key in the Requisitions table.

*The problem is that while someone has the form open and displaying the "next available Req Number", which will be printed for signatures, someone else may open the form to submit a Purchase Req and it will grab the very same "next available Req Number" since the first one has not been submitted yet.

I need something like a Session Variable, but that the Server is aware of so that each time the form is opened it gets a different number.

Here is a scenario. The last Req # in the DB is 29. User A opens the form and Req # 30 is printed on the form. Currently if User B opens the form before User A submits his, then User B will have Req # 30 also. Not good.

What should happen is when User A opens the for he gets Req #30, then User B opens the form and gets Req # 31, User C opens his form at the same time as the others and gets Req #32.

User A eventually submits his form and record 30 is added to the table.
Users B and C abort without submitting the form at all.
Next day (whenever) any user opens the form, he gets #31

I do see the issue where User A submits #30, User B aborts and User C submits what he thinks is #32 but it goes into the DB as Identity record #31. Dang. Hmmm, also if User C submits his first then the record numbers will be out of order. I guess I need a better solution. Any ideas?

You could use a control table in your database that tracks the next requisition number, which you would store in your table separately from the actual ID of the record. Each time you retrieve the next number you increment it so that the next call will always be one further on.

That way you keep the Identity column as an auto-incrementing number that the user never sees, and you store a specific requisition number against the record.

instead, dont show orderid until it is submitted to db
in db create a stored proc and in this sp, either run a query to get max+1 (or use identity and insert with null as id and get identity on this table to find the inserted id - i suggest this)
once you insert the record, you will have the orderid and you can return this to page, and show it to user...

Yeah, that's just about what a colleague and I were just discussing. The control table would use auto incrementing "Identity" values and the main order table would not. The main table would have to accept whatever order number was submitted.

We also discussed making the form create a new order record when the form is opened and when it's submitted do an UPDATE to insert the field values. The problem I see with that is you'd have an empty record every time someone just looked at the form then closed it unless you could DELETE that record if it wasn't "Submitted". Is that possible (or practical)?

one more thing can be done...
you do as you have suggested i.e. insert a row the update it and delete in case user cancel the request. but while getting the new id search for the gaps and assign the gap id to the new record

when you use autoincrement column in your table, there will be gaps only if the insert statement fails somehow... other than that there wont be any gaps... if gaps is not important us the one I suggested before...

if you DO NOT want any gaps, when you try to insert the record, find the min gap and use that one as new id for inserted record...

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